File Server Capacity Tool (FSCT) 1.0

What is “FSCT”?

New builds of Microsoft Windows are produced almost every day for internal development and testing. In order to detect performance regressions as soon as possible, those builds have to be evaluated and compared to their predecessors as well as previous public releases. A range of performance tests are used for these comparisons, including one called “FSCT” (which stands for File Server Capacity Tool). FSCT was developed by the Windows Server Performance team as a tool capable of simulating multiple concurrent users accessing a file server using CIFS/SMB/SMB2. Its architecture allows for usage of “workloads”. Each workload consists of a set of basic scenarios (e.g. upload of a file using Explorer, upload of a file using xcopy, Microsoft Word opening a file, etc.), information on how often those scenarios should be performed by users, and what files on the file server under test should be used. FSCT measures a file server’s capacity for a given workload. This includes the highest throughput the server can sustain and the maximum number of active users the server can support. FSCT also reports on server resource utilization, which can help identify performance bottlenecks such as network or storage bandwidth or CPU utilization.

The HomeFolders workload

The publically available version of “FSCT” comes with a single workload called HomeFolders. It was created by working with Microsoft IT administrators to capture Event Tracing for Windows (ETW) traces from real, heavily accessed file servers and their clients. The data included server side traces, client API traces and network traces, to capture the requests type distribution, parameters distribution, file set characteristics, and connection characteristics. Finally, the workload was created and tested to achieve approximately the same usage patterns found in the traces.

The workload development effort included creating the scenarios, creating the file sets and defining the number of runs per user per hour of each scenario. It is important to mention that “FSCT” and the HomeFolders workload were developed independently. The “FSCT” architecture allows for the creation of custom workloads and scenarios, as well as tweaking the existing workloads. However, as mentioned previously, only the HomeFolders is included in the initial release of “FSCT”.

You can find more information on FSCT at